An electroluminescent (EL) lamp generally comprises a layer of phosphor disposed between two electrodes at least one of which is light-transmissive. A dielectric is also disposed between the electrodes, so the EL lamp functions essentially as a capacitor. When a voltage of alternating current is applied across the electrodes, the phosphor material is activated and emits light.
EL lamps may be manufactured as discrete cells or as large panels or rolls and either on rigid or flexible substrates. In addition, each component of the lamp may be formed as a separate layer, such as a foil sheet serving as an electrode and a planar dielectric sheet, with the layers later laminated together as by heat and pressure. Alternatively, the layers may be combined into overlapping coatings printed on a substrate, as is the case for a layer of light-transmissive conductive ink serving as a top electrode followed by a layer of phosphor ink in a dielectric matrix and then another conductive ink coating serving as a back electrode. EL lamps have found widespread uses, e.g. in signs, watch faces, and as backlighting for keyboards.
Membrane switches are also well-known. A membrane switch is generally constructed of two spaced-apart electrically conductive surfaces on separate substrates. At least one substrate is flexible. For example, each conductive surface may be a pattern of electrically conductive ink. A spacer layer with an aperture is positioned between the two facing conductive surfaces. When a user depresses the flexible substrate containing one of the conductive surfaces, the two conductive surfaces come into contact thereby causing activation of the switch and closing a circuit. Membrane switches have also been used in a variety of devices, such as on keyboards and control panels for appliances. See, e.g., U.S. Pat. No. 4,683,360 to Maser for a membrane switch combined with an EL lamp panel.
An object of the present invention is to provide a device utilizing EL lamps and membrane switches for imparting educational and entertainment information in an interactive manner.